The instant invention relates generally to an annulus pressure operated ratchet device and more particularly, but not by way of limitation, to such a device which is used to set a packer in a well bore.
Sometimes it may be desirable to set a packer in a well bore without the use of metal slips which include teeth that engage the well bore in order to effect packer setting. For example, sometimes a portion of the original metal casing in a well bore may become corroded to the point where there is fluid communication between the bore and the adjacent zone as a result of the corrosion. In such cases it may be necessary to repair the casing to permit well treatment or production without loss of well fluids due to casing corrosion.
One method of casing repair entails cementing plastic or fiberglass casing inside the corroded casing as a liner to restore casing integrity. Such a liner typically extends downwardly to the production zone of interest. In order to produce or inject additional corrosive fluids, a packer suspended from a tubing string must be set inside the plastic casing to prevent further contact of the corrosive elements with the metal casing above the liner. A conventional packer which is set by engaging metal slip teeth against a casing cannot be used to set a packer in a plastic or fiberglass liner.
The instant invention comprises a mandrel having a tubular sleeve slidingly received thereover. Ratchet means are disposed between the sleeve and the mandrel for effecting ratcheting action therebetween in response to movement of the sleeve relative to the mandrel. Piston means slidably mounted on the mandrel adjacent the sleeve is operable to slide the sleeve responsive to annulus pressure.
In one aspect of the invention, an elastomeric packer is disposed about the mandrel adjacent the sleeve and is compressed responsive to movement of the sleeve thereagainst. Another aspect of the invention includes an annular shoulder against which the packer is compressed. The shoulder is threadably engaged with the mandrel by a left-hand thread which enables release of packer compression responsive to right-hand mandrel rotation.